KR20050093769A - Method for producing drawn coated metals and use of said metals in the form of a current differenciator for electrochemical components - Google Patents

Abstract

The invention relates to a method for producing coated drawn metal. The inventive method is characterised in that the coating is applied to a closed metal foil which is transferred to a drawn metal after the coating process only. In particular, the coating can be embodied in such a way that it improves the adhesion of said drawn metal to electrode material and/or the surface electronic conductivity thereof. The inventive drawn metals are successfully used in the form of current derivators in/for an anode foil or in/or a cathode foil, for example for an electrochemical cell, in particular for a storage battery.

Description

Coated rolled metal for manufacturing coated rolled metal and for use as current induction device for electrochemical components.

The invention relates in particular to coated rolled metals, which are suitable as current induction devices in electrochemical parts, in particular in water-insoluble electrochemical cells.

The non-aqueous electrochemical cell is typically a lithium battery. This has already been known in various embodiments for a long time and has been described in various ways. The construction of such a battery generally faces a cathode, which is a stable lithium inclusion compound, with an anode made of lithium metal or graphite. Both electrodes are separated by a separator. The whole system is passed by an electrolyte that ionizes lithium ions. This electrolyte is generally a lithium salt dissolved in one or a plurality of organic solvents. During charging or discharging, lithium ions are moved between the electrodes.

In order to solve the problem of incompatible electrolyte solution inside the battery body, it has been successfully attempted to implement the electrode and the separator in the form of a film. Such films are characterized by the addition of high porosity or the addition of suitable polymers that are gelficated into a liquid in which the liquid electrolyte is not fixed.

In addition to the electrochemical components described, there is a need for a current induction device, which is a component that collects, discharges and makes it suitable for use with electrical devices. The current inducing device is a metal formed of a film or a rolled metal. Current induction devices must meet a set of conditions. That is, (a) it must be electrochemically stable against corrosion, (b) have good contact with each electrode to ensure low boundary resistance, (c) have a light weight to ensure high energy density, (d) It preferably has elastic properties to compensate for current variations upon occlusion or release of lithium ions in the electrode during operation. For conventional systems involving lithium cobalt oxide as the cathode material and graphite as the anode material, aluminum or copper has proved to be suitable for metals fixed in the electrochemical environment of the battery. However, the described method is not limited to the metals.

The production of the rolled metal is briefly described below. The method is shown schematically in FIG. 1. A metal film 1 of suitable thickness is provided to the stamping tool 2 having a stamping pattern and then stretched (3). The design and stretching strength of the stamping pattern determine the structural data of the rolled metal, such as the area of the seam, the opening diagonal and the area of the open face.

The advantages of using rolled metal as the current induction device are clear. That is, since the metal has an open porous structure compared to the film, it is possible to reduce the weight of the current inducing device, which has an advantage in terms of energy density. The rolled metal is thus elastic so that current fluctuations can occur during occlusion and release of lithium in the electrode without interlayer separation. Interlayer separation will also reduce the cycle (charge / discharge) persistence of the battery.

Other manufacturing techniques benefit from the use of rolled metal in lithium-polymer-storage batteries. The accumulator type is generally manufactured as follows. That is, the electrodes are either deposited directly on the metal film (see US 6 306 215) or by lamination under pressure and, in some cases, in the current inducing device under temperature action (DE 199 52 335). Then, in the second step, a complete compound consisting of three films is produced by lamination or tightly wound coil technology, an anode with a current induction device, a separator and a cathode with a current induction device. The compound is filled with electrolyte solution. The electrolyte solution should be evenly distributed over the entire film compound. This is done by capillary forces. This process is often supported by the additional formation of voids. Further formation of the voids is achieved by the addition of plasticizers to the electrode and separator material, which are then laminated together with other components and separated again by solvent. The finished metal film makes the electrolyte solution very difficult to penetrate into the battery. That is, the process period is extended. The use of open dense rolled metal thus offers process technical advantages.

In order to obtain good adhesion and low boundary resistance at the boundary between the metal current inductor and the stacked electrodes, the current inductor is preferably made to be covered by a thin layer of adhesive before being provided to the electrode, in particular in this case the adhesive layer It is desirable to have silver conductivity. Deposition techniques and suitable configurations of such adhesives have been proposed in the prior art. It includes coating in the form of a paste by spin coating, dipping or spreading a current inducing device or liquid made of rolled metal or other induction device with small holes (US 6 306 215 and US 5 824 120), carbon powder and Deposition using an electrostatic force (US 5 542 163) of a layer comprising a polymer with improved adhesion, or a plasma polymerization process for depositing a conductive, polymeric, adhesively improved material into a storage battery (US 6 007). 588). As mentioned above, to produce void volume for the electrolyte, all publications mentioned are made up of an electrode material comprising a plasticizer which is then washed together from the cell after the individual components (electrode and separation layer or film, current inducing device) are stacked together. Describe chemical cells. The coating layer may be deposited by appropriate suspension using printing technique methods. Suitable suspensions are sold. For example, printing roll technology methods such as Reverse Roll Coating are used. Suspensions are slightly water-like solvents, usually consisting of a carbon / polymer mixture.

Problems arise in the practical transformation of the coating method using the printing technology method. The coating layer of the suspension is generally about 1-2 μm. The printing coating method can always identify defective wetting which results in non-uniform distribution of the suspension on the metal. Thus, an electrochemical component with a rolled metal coated in this way, for example in an elevated wetting position with an increase in boundary resistance or even in a current inducing device, results in an adverse effect on the life of the component during operation of the battery. Contact loss between electrodes occurs. However, thicker adhesive layers are prohibited in this regard due to the undesirable reduction in energy density.

Additional technical problems arise when using printing techniques to deposit adhesive layers. In order to introduce the film correctly during the coating, the introduction of the metal film to be coated must be made by a multidirectional induction roller. In addition, the film must be kept under a certain mechanical stress in the circular operation by the coating machine. The use of a finished metal film such as aluminum or copper, for example, shows no technical problems at about 10-15 μm film thickness, while the rolled metal already tends to crack at small tensile stresses. Typical thickness of the rolled metal is 50 μm or less. Machines specially equipped for coating layers of rolled metal only have strong problems in yield due to such cracks. Conversion to thicker rolled metals, due to process safety reasons, is prohibited because the energy density is undesirably reduced by thick coating layers.

It is an object of the present invention to provide an improved yield of the process described above for the production of coated rolled metal, by which the upper and lower sides of the thinner rolled metal can be coated very thinly with a conductive adhesive.

This object is achieved by a method in which a closed metal film is first coated and then converted to a rolled metal. This has the advantage that the coating layer is deposited on a mechanically fixed metal film, so that a product having the required properties can be produced at a high yield and the rejects can be greatly reduced. The coating consists of one or both sides. It is very surprising that the coating layer deposited with the film falls off upon rolling in the performance of the method. This could never have been expected. This is because the coating layer is sufficiently elastic and the polymer adhesiveness is good enough that the layer does not fall apart even when the metal under the rolled coating layer is widely spread and deformed.

In addition, very surprisingly, other advantages of the present invention have been identified, which extend the life of the stamping tool in the manufacture of rolled metal. This is based on the fact that a common adhesive is a suspension containing graphite, which acts as a lubricant during the stamping process, contributing to prolonging the duration of the stamping tool.

1 is a sequence of laminations suitable for a battery

2 is a plan view of the lamination;

3 is a schematic diagram of rolled metal production.

4 is a graph according to the actual capacitance of a battery with a rolled metal produced according to the invention as an induction device.

5 is a comparison of the actual capacitance of a battery with an induction device manufactured in general and the actual capacity of a battery with a rolled metal produced as an induction device according to the invention.

It is particularly preferred if the metal film is corona surface treated prior to the coating process. This is because such measures further improve the adhesion of the coating layer on the rolled metal.

 It is desirable to stretch the metal so that the short diagonal is about 1 mm and the long diagonal is about 2 mm in length. Increasingly stronger, depending on the flexibility of the coating material used, ie in most cases the coating may be separated.

As a material for the coating of a metal film to be subjected to a later stretching process, a material is achieved that achieves certain properties that require a rolled metal for later use. Certain properties are good adhesion and good conductivity, in particular for rolled metals used as current induction devices. However, it should be clear that the method according to the invention is not limited to the production of coated rolled metal for current collectors and current induction devices. Rather, it is not essential that precise and thinly coated thin rolled metal can be used wherever it is used, and that the openings produced during stamping and stretching are also laterally coated.

Examples of suitable materials for coatings with good adhesion and conductivity are graphite or other suitable carbon materials and organic polymers for improved adhesion. The carbon material is provided in a binder such as, for example, an organic polymer suspension, which may subsequently be dried, cured or further polymerized at the surface. As an example, EB-012 from Acheson, USA, contains a thermoplastic binder in graphite suspension. Another example is a suspension containing silver instead of graphite. The binder can be, for example, an epoxy, thermoplastic, hard ISF, vinyl hardener, cellulose or fluorine elastomer. However, other suitable materials may be used in place of the graphite suspension, for example, when providing the mentioned properties, such as conductive organic polymers such as Poly Vinyl Pyrrolidon (PVP). In addition, polymer suspensions which are graphitized after being deposited on metal are well suited for coating.

The process according to the invention has been invented in view of the poor quality of the rolled metal coated with the printing technique. However, it is not limited to specific coating techniques. Instead of coating by printing techniques, for example, rotary coating, roll coating, knife coating, dip coating, electrostatic stimulation (powder coating) or plasma methods can be used, in particular as known in the above-mentioned prior art.

The rolled metal produced according to the present invention differs from the prior art in that the openings produced during stamping and stretching are not side coated. At least there are no disadvantages in the use of current collectors and current induction devices.

Rolled metals produced or manufacturable in accordance with the present invention are particularly electrochemical which does not add plasticizers which have to be separated again in subsequent cleaning processes to the electrode material and / or separator material in order to create the voids necessary to absorb the electrolyte liquid. Suitable for use in batteries This method of preparation described in US Pat. No. 5,456,000 or 6 063 519 requires chemical stability to the wash liquor as an additional condition for the adhesive layer. Partial separation of the electrode film of the current induction device may occur upon cleaning of the plasticizer, which has a negative effect on the cycle duration and impedance of the battery. It is therefore particularly preferred by the present invention that the electrochemical component is produced with a current inducing device made according to the invention, wherein the electrodes and separators of the component are produced without the cleaning and separating of the plasticizer.

The invention is explained in detail in the accompanying drawings and in the examples which follow.

Example 1

Copper rolled metal

Both sides of the 50 μm rigid copper film are coated with a commercially available suspension EB 012 (dictropic graphite suspension in a thermoplastic plastic binder) available from Acheson Colloids B. V .. In order to control the optimum viscosity for the coating, the solids content in the suspension is reduced from 30% to 20% by adding water. On one side by means of a simple lamination roll, the front side is first coated and the second side is coated. Copper film is a commercially available standard film for battery use. Wet coating strength is about 20 μm at 2.5 m / min operating speed. Drying takes place at about 80 ° C. The layer thickness of the adhesive layer after drying is 4 m. The film so coated subsequently is subsequently treated with a rolled metal. The stretch is adjusted so that the short diagonal length is 1 mm and the long diagonal length is 2 mm. The material obtained did not separate and crack in the metal and could still be used 100%.

Comparative Example 1

Example 1 was repeated and the stretch was adjusted so that the length of the short diagonal was 1.5 mm and the length of the long diagonal was 3 mm. The product showed cracks in the coating. At many locations the cracks fell off. The defective rate in the area was about 30%.

Comparative Example 1a

Example 1 This copper film was first converted to a rolled metal and this was repeated assuming it was coated as described. The resulting material was distributed with a number of locations with cracks and peeled off coating layers. The rolled metal was used only once during six rollings for subsequent processing to be used in the current induction device. In total, more than 50% of the rolled metal area was damaged.

Example 2

As described earlier, both sides of a 50 μm thick aluminum film are coated with a commercially available suspension EB 012 from Acheson Colloids B. V .. The content of solids in the suspension to adjust the optimum viscosity for the coating is reduced from 30% to 20% by adding water. On one side by means of a simple lamination roll, the front side is first coated and the second side is coated. Copper film is a commercially available standard film for use in batteries. Wet coating strength is about 20 μm at 2 m / min operating speed. Drying takes place at about 80 ° C. The layer thickness of the adhesive layer after drying is 4 m. The film so coated subsequently is subsequently treated with a rolled metal. The stretch is adjusted so that the short diagonal length is 1 mm and the long diagonal length is 2 mm. The material obtained did not separate and crack in the metal and could still be used 100%.

Comparative Example 2

Example 2 was repeated and the stretch was adjusted so that the short diagonal length was 1.5 mm and the long diagonal length was 3 mm. The product showed cracks in the coating. At many locations the cracks fell off. The defective rate in the area was about 25%

Example 3

Anode film

For production of the anode film, 1.7 g spherical graphite MCMB was mixed with carbon black (acetylene block) and polyvinylidene fluoride (PVDF-HFP) containing 0.2 g of copolymer with 2 g of acetone. And a uniformly dispersed paste by a cutting stirrer. This is subsequently transferred from the lantern slide to the film by a doctor blade. After the solvent is evacuated, a self-supporting film remains, which is removed by the lantern slide. The thickness of the dried layer is about 100 μm.

Example 4

Cathode film

Cathode films of the same size corresponding to the anode film are prepared in the following configuration: 3.6 g LiCoO ₂ is mixed with 0.2 g conductive carbon black (acetylene black), 0.2 g PVDF and 4 g acetone. The layer thickness is likewise 100 μm.

Example 5

Separator film

Ceramic fillers (lithium aluminum titanium phosphate; Li ₁ , ₃ Al ₀ , ₃ Ti ₁ , ₇ (PO ₄ ) ₃ ) as described (3) about 50 μm separator film with 0.5 g PVDF-HFP and 2.4 g acetone Is processed into.

Example 6

Lamination

Laminating the electrode film on the induction grating is done in a rolling laminator. The film is preheated at 60 ° C. and spun up at 236 kp compression. The machine running speed is 40 mm / s. Subsequent tape tests show that each film adheres well in the corresponding induction grating. In a second lamination step, three device anodes including a copper induction grating, a cathode including an aluminum induction grating, and a separator film are laminated together. Likewise, at a lamination temperature of 160 ° C. and an operating speed of 20 mms, the force is about 16 kp. The configuration of the battery body is shown in FIGS. 1 and 2. 1 is a cross section of a battery, while FIG. 2 shows a plan view of the battery body. In FIG. 1 an aluminum rolled metal 4 is shown comprising a cathode film 5 and a separator film 6, coated with an adhesive. The opposing electrode consists of an adhesive coated copper rolled metal 8, comprising a laminated anode film 7. 4 shows an aluminum rolled metal. After packaging with film, two contact tongues 9 are guided laterally for contact with the battery.

Example 7

Manufacturing location of the battery

The battery is mounted into a plastic coated aluminum film so that the electrical contacts of the current inducing device can be guided outward. Subsequently, a commercially available conductive saline LP30, which is commercially available in a waterfree protective gas furnace, is provided through absorption into the laminated film compound. The bag is sealed. A storage battery is then formed and electrically surveyed. High cycle persistence under C-rate load. Its characteristic curve is shown in FIG. Maintain more than 80% of output capacitance after 300 charge and discharge cycles.

The capacitance of the battery is compared with a battery in which the induction device is made of conventional, coated rolled metal (defect-free). As shown in Fig. 5, the output data of both batteries is actually the same. The process according to the invention thus generally provides a coating having the same quality as the coated rolled metal.

Claims (17)

The coating is provided in a closed metal film, and the film is converted to the rolled metal after coating. The method of claim 1, wherein the coating improves the adhesion of the rolled metal and / or the conductivity at the surface of the rolled metal as compared to the electrode material. The method of claim 1 or 2, wherein the coating comprises graphite or other carbon material, or an organic or inorganic-organic polymer, with a binder that improves adhesion. 4. The method of any one of claims 1 to 3, wherein the metal is copper or aluminum. The method of claim 1, wherein the metal film is corona surface treated before being coated. The method according to any one of claims 1 to 5, wherein the length of the short diagonal is up to 1 mm and the length of the long diagonal is up to 2 mm when the metal film is converted to the rolled metal. The method according to any one of claims 1 to 6, characterized in that the coating is provided using a printing technique by spin, coating, rolling, doctor blade, immersion coating, electrostatic powder coating or by a plasma process. How to. Coated rolled metal obtainable by the method according to any of claims 1 to 7. Coated rolled metal obtained according to any one of the preceding claims. 10. The coated rolled metal according to claim 8 or 9, wherein the coating improves the adhesion of the rolled metal and / or the conductivity at the surface of the rolled metal as compared to the electrode material. The coated rolled metal of claim 10, wherein the coating is deposited by a suspension comprising graphite or other carbon material and a binder, or by an organic or inorganic-organic polymer that is subsequently graphitized. The coated rolled metal according to claim 10 or 11 used as an induction device in an anode film or for an anode film, or in a cathode film or for a cathode film. 13. The coated rolled metal according to claim 12, wherein the current inducing device and the anode film or the cathode film are laminated together. The coated rolled metal according to claim 12 or 13, wherein the anode film or the cathode film is produced without using a plasticizer. Coated rolled metal according to claim 10 or 11 for use in electrochemical cells, in particular accumulators. 16. The coated rolled metal according to claim 15, wherein the battery is a lithium technology battery. 17. The coated rolled metal according to claim 16, wherein the battery is made by a technique that does not require plasticizer addition and subsequent cleaning of the plasticizer.